1. Field of the Invention
The present invention relates to a method of electronic fuel injection control for an internal combustion engine. More particularly, the present invention relates to a method for fuel injection control which causes fuel to be delivered through a variable number of pulse fragments, wherein the width of each pulse fragment is based upon the current engine operating conditions and each pulse fragment is delivered at a variable delivery angle which is also dependant upon the current engine operating conditions.
2. Related Art
Modern automotive engines typically employ one or more fuel injectors for delivering fuel from a fuel source to the cylinders of an internal combustion engine. In electronically controlled fuel injection systems, the fuel injectors are generally operated by electronic pulses which cause the respective fuel injector to dispense an amount of fuel in proportion to the width of the pulse.
Conventionally, the pulse width for an injector is calculated once in response to various engine dynamics which include throttle position, engine speed, manifold pressure, airflow, temperature and the level of oxygen in the exhaust. Although the delivery of fuel could take place over a range of acceptable crankshaft positions (hereinafter referred to as the fueling window), the delivery of the pulse is commonly timed to a specific crankshaft position within the fueling window. Typically, the pulse width calculation is performed well in advance of the time at which the pulse is to be delivered; the pulse is generally delivered at an early point within the fueling window.
While these prior arts methods have performed well under steady-state conditions, several problems have been noted with their response to transient conditions, such as changes in throttle position. When the throttle is rapidly closed, for example, these prior art fueling methods will cause the engine to be fueled with excess fuel since the width of the pulses had been based upon a previous, more open throttle position. As such, the engine will experience a rich-burn condition which adversely affects fuel economy and exhaust emissions.
Similarly, when the throttle is opened rapidly, these prior art fueling methods will cause an insufficient level of fuel to be delivered to the engine for combustion since the width of the pulses had been based upon a previous, more closed throttle position. As such, the engine will experience a lean-burn condition which adversely affects exhaust emissions.
Improved methods, such as the one in commonly owned U.S. Pat. No. 5,003,953, have been disclosed. This method, for example, generates a second pulse in response to a rapidly opening throttle. The width of the second pulse is calculated subsequent to the delivery of the primary pulse and is delivered so as to coincide with the termination of the fueling window. While this method has been successful in improving the fuel economy and exhaust emissions, several problems have been noted. As with the other prior art methods, this method is not capable of causing a reduction in the level of fuel delivered to the engine in response to the detection of a rapidly closing throttle. Also, the delivery of the second pulse at the end of the fueling window without regard to various other engine dynamics can be detrimental to exhaust emissions.
Consequently, there remains a need in the art for a method for controlling the amount and timing of fuel delivered by a multi-port fuel injection system that improves the transient response of the system during times where the fueling requirements are increasing or decreasing so as to improve performance and emissions.